Other Important TCPIP Standards

1
Other Important TCP/IP Standards

• Domain Name System (DNS)
• Autoconfiguration Protocols

2
Domain Name System (DNS)

• Only IP addresses are official
• e.g., 128.171.17.13
• These are 32-bit binary numbers
• Only they fit into the 32-bit destination and
  source address fields of the IP headers

IP Packet
32-bit Source and Destination Addresses
(110011...)
3
Domain Name System (DNS)

• Users typically only know host names
• e.g., voyager.cba.hawaii.edu
• More easily remembered, but
• Will not fit into the address fields of an IP
  packet

IP Packet
NO
voyager.cba.hawaii.edu
4
Domain Name System (DNS)

• Users computer sends a DNS host the target
  hosts host name in a DNS Request message
• DNS host returns the target hosts IP address in
  DNS Response message

Voyager.cba. hawaii.edu
User PC Internet Layer Process
DNS Host
128.171.17.13
5
Domain Name System (DNS)

• Subtlety
• Organizations or ISPs have local DNS hosts
• These hosts must know only local host names and
  IP addresses
• For other host names, local DNS host passes
  request to another DNS host

User PC Internet Layer Process
Local DNS Host
Remote DNS Host
6
Domain Name System (DNS)

• Subtlety
• Remote DNS host passes information back to the
  local DNS host
• Local DNS host passes information back to user PC
• Browser only talks to local DNS host

User PC Internet Layer Process
Local DNS Host
Remote DNS Host
7
Domain Names

• Internet uses hierarchical naming
• A domain is a collection of resources managed by
  an organization
• Generic top level domains (gTLD) by type of
  organization
• .com for commercial organizations
• .edu for educational institutions
• National top level domains (nTLDs) by country
• .UK United Kingdom
• .AU Australia

8
Domain Names

• Organizations are given second-level domain names
• Microsoft.com
• Hawaii.edu
• JAIMS.org
• panko.com
• Whitehouse.gov
• Also can have second-level domains for products
  (nameofnewmovie.com)

9
Domain Names

• Organizations can create lower-level domain names
• cba.hawaii.edu (for the College of Business
  Administration)
• The lowest level domain name is the host name for
  an individual host or router
• www.cba.hawaii.edu
• www.microsoft.com
• www.panko.com

10
Autoconfiguration

• Every computer attached to the Internet is a host
• Including desktop PCs
• Every host must have an IP address
• Some hosts, such as routers and webservers, get
  permanent IP addresses
• So that they can be found easily

11
Autoconfiguration

• User PCs do not need permanent IP addresses
• They only need to be found within a use session
• They usually are given temporary IP addresses
  each time they use the Internet
• They may get a different IP address each time
  they use the Internet

12
Autoconfiguration

• Request-Response Cycle
• User software requests IP address for the user PC
  in Autoconfiguration Request message
• Autoconfiguration Response message contains
  temporary IP address to use in current session

Autoconfiguration Request
User PC
Autoconfiguration Host
Temporary IP Address in Autoconfiguration Response
13
Autoconfiguration

• Most popular autoconfiguration protocol is DHCP
• Dynamic Host Configuration Protocol
• Built into Windows after Win 3.1
• Supplies host with temporary IP address
• DHCP can give more information too
• Usually gives IP address of a default gateway
  (Microsoft terminology for router)
• Can give IP address of a local DNS host
• Can give other information